The Effects of Macronutrient Enrichments (ammonium) on the Distribution of Four Bioactive Trace Metals (Cd, Mo, Ni, Cu) in Seawater and Planktonic Biomass.

Environmental impacts of aquaculture can be widespread and serious, and one of the problems connected to this activity is the release of waste in the form of macronutrients. One important aspect is the potential of a shift in the available nitrogen form from nitrate to ammonium. This has the potential of causing harmful algal blooms, and changing the composition of pelagic microbial communities. Because trace metals are linked to enzymatic transformations of nitrogen it can be expected that a shift in the available nitrogen form to also change the cycling of trace metals in the water column and the microbial uptake. This work presented in this thesis has been part of the large collaborative WAFOW project, and was carried out at the Huinay Scientific Field Station in the Comau Fjord (Northern Patagonian region of Chile). The experiment was designed to follow changes in different variables as a gradient of ammonium was added to different bodies of water (mesocosms). Two types of water were studied (surface and ~10 m depth), and five treatments with increasing ammonium flux were carried out for each water type. In this thesis the variations in the distribution of four different trace metals (Cd, Mo, Ni and Cu) with an increasing ammonium flux has been studied. Samples were analyzed for chelex labile and DGT labile forms of the metals, as well for metal concentration in different size fractions of particles. The enrichment by ammonium caused a bloom in biomass, and caused changes in the distribution of all four metals studied. Most of the metals showed decreasing chelex labile and DGT labile concentration with rising ammonium concentration. For cadmium there was a marked increased uptake per g carbon up to a certain point of ammonium enrichment, and a marked decreased uptake per g carbon when very high amounts of ammonium were added. This suggests that the very high ammonium enrichment scenario somehow has had an inhibiting effect on phytoplankton cadmium uptake. For molybdenum there was a decreasing uptake per g carbon with increasing ammonium flux. This is probably caused by a decreased need for molybdenum in enzymatic transformations of nitrogen when ammonium is supplied in place of nitrate

The Effects of Macronutrient Enrichments (ammonium) on the Distribution of Four Bioactive Trace Metals (Cd, Mo, Ni, Cu) in Seawater and Planktonic Biomass.

Environmental impacts of aquaculture can be widespread and serious, and one of the problems connected to this activity is the release of waste in the form of macronutrients. One important aspect is the potential of a shift in the available nitrogen form from nitrate to ammonium. This has the potential of causing harmful algal blooms, and changing the composition of pelagic microbial communities. Because trace metals are linked to enzymatic transformations of nitrogen it can be expected that a shift in the available nitrogen form to also change the cycling of trace metals in the water column and the microbial uptake. This work presented in this thesis has been part of the large collaborative WAFOW project, and was carried out at the Huinay Scientific Field Station in the Comau Fjord (Northern Patagonian region of Chile). The experiment was designed to follow changes in different variables as a gradient of ammonium was added to different bodies of water (mesocosms). Two types of water were studied (surface and ~10 m depth), and five treatments with increasing ammonium flux were carried out for each water type. In this thesis the variations in the distribution of four different trace metals (Cd, Mo, Ni and Cu) with an increasing ammonium flux has been studied. Samples were analyzed for chelex labile and DGT labile forms of the metals, as well for metal concentration in different size fractions of particles. The enrichment by ammonium caused a bloom in biomass, and caused changes in the distribution of all four metals studied. Most of the metals showed decreasing chelex labile and DGT labile concentration with rising ammonium concentration. For cadmium there was a marked increased uptake per g carbon up to a certain point of ammonium enrichment, and a marked decreased uptake per g carbon when very high amounts of ammonium were added. This suggests that the very high ammonium enrichment scenario somehow has had an inhibiting effect on phytoplankton cadmium uptake. For molybdenum there was a decreasing uptake per g carbon with increasing ammonium flux. This is probably caused by a decreased need for molybdenum in enzymatic transformations of nitrogen when ammonium is supplied in place of nitrate

Iron Speciation and Physiological Analysis Indicate that Synechococcus sp. PCC 7002 Reduces Amorphous and Crystalline Iron Forms in Synthetic Seawater Medium

Cyanobacteria have high iron requirements due to iron-rich photosynthetic machineries. Despite the high concentrations of iron in the Earth’s crust, iron is limiting in many marine environments due to iron’s low solubility. Oxic conditions leave a large portion of the ocean’s iron pool unavailable for biotic uptake, and so the physiochemical properties of iron are hugely important for iron’s bioavailability. Our study is the first to investigate the effect of iron source on iron internalization and extracellular reduction by Synechococcus sp. PCC 7002. The results indicated that the amorphous iron hydrolysis species produced by FeCl3 better support growth in Synechococcus through more efficient iron internalization and a larger degree of extracellular reduction of iron than the crystalline FeO(OH). An analysis of dissolved iron (II) indicated that biogenic reduction took place in cultures of Synechococcus grown on both FeCl3 and FeO(OH)

Iron Speciation and Physiological Analysis Indicate that <i>Synechococcus</i> sp. PCC 7002 Reduces Amorphous and Crystalline Iron Forms in Synthetic Seawater Medium

Cyanobacteria have high iron requirements due to iron-rich photosynthetic machineries. Despite the high concentrations of iron in the Earth’s crust, iron is limiting in many marine environments due to iron’s low solubility. Oxic conditions leave a large portion of the ocean’s iron pool unavailable for biotic uptake, and so the physiochemical properties of iron are hugely important for iron’s bioavailability. Our study is the first to investigate the effect of iron source on iron internalization and extracellular reduction by Synechococcus sp. PCC 7002. The results indicated that the amorphous iron hydrolysis species produced by FeCl3 better support growth in Synechococcus through more efficient iron internalization and a larger degree of extracellular reduction of iron than the crystalline FeO(OH). An analysis of dissolved iron (II) indicated that biogenic reduction took place in cultures of Synechococcus grown on both FeCl3 and FeO(OH)

Iron Speciation and Physiological Analysis Indicate that Synechococcus sp. PCC 7002 Reduces Amorphous and Crystalline Iron Forms in Synthetic Seawater Medium

Cyanobacteria have high iron requirements due to iron-rich photosynthetic machineries. Despite the high concentrations of iron in the Earth’s crust, iron is limiting in many marine environments due to iron’s low solubility. Oxic conditions leave a large portion of the ocean’s iron pool unavailable for biotic uptake, and so the physiochemical properties of iron are hugely important for iron’s bioavailability. Our study is the first to investigate the effect of iron source on iron internalization and extracellular reduction by Synechococcus sp. PCC 7002. The results indicated that the amorphous iron hydrolysis species produced by FeCl3 better support growth in Synechococcus through more efficient iron internalization and a larger degree of extracellular reduction of iron than the crystalline FeO(OH). An analysis of dissolved iron (II) indicated that biogenic reduction took place in cultures of Synechococcus grown on both FeCl3 and FeO(OH)

From the Ocean to the Lab—Assessing Iron Limitation in Cyanobacteria: An Interface Paper

Iron is an essential, yet scarce, nutrient in marine environments. Phytoplankton, and especially cyanobacteria, have developed a wide range of mechanisms to acquire iron and maintain their iron-rich photosynthetic machinery. Iron limitation studies often utilize either oceanographic methods to understand large scale processes, or laboratory-based, molecular experiments to identify underlying molecular mechanisms on a cellular level. Here, we aim to highlight the benefits of both approaches to encourage interdisciplinary understanding of the effects of iron limitation on cyanobacteria with a focus on avoiding pitfalls in the initial phases of collaboration. In particular, we discuss the use of trace metal clean methods in combination with sterile techniques, and the challenges faced when a new collaboration is set up to combine interdisciplinary techniques. Methods necessary for producing reliable data, such as High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS), Flow Injection Analysis Chemiluminescence (FIA-CL), and 77K fluorescence emission spectroscopy are discussed and evaluated and a technical manual, including the preparation of the artificial seawater medium Aquil, cleaning procedures, and a sampling scheme for an iron limitation experiment is included. This paper provides a reference point for researchers to implement different techniques into interdisciplinary iron studies that span cyanobacteria physiology, molecular biology, and biogeochemistry

From the Ocean to the Lab—Assessing Iron Limitation in Cyanobacteria: An Interface Paper

Iron is an essential, yet scarce, nutrient in marine environments. Phytoplankton, and especially cyanobacteria, have developed a wide range of mechanisms to acquire iron and maintain their iron-rich photosynthetic machinery. Iron limitation studies often utilize either oceanographic methods to understand large scale processes, or laboratory-based, molecular experiments to identify underlying molecular mechanisms on a cellular level. Here, we aim to highlight the benefits of both approaches to encourage interdisciplinary understanding of the effects of iron limitation on cyanobacteria with a focus on avoiding pitfalls in the initial phases of collaboration. In particular, we discuss the use of trace metal clean methods in combination with sterile techniques, and the challenges faced when a new collaboration is set up to combine interdisciplinary techniques. Methods necessary for producing reliable data, such as High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS), Flow Injection Analysis Chemiluminescence (FIA-CL), and 77K fluorescence emission spectroscopy are discussed and evaluated and a technical manual, including the preparation of the artificial seawater medium Aquil, cleaning procedures, and a sampling scheme for an iron limitation experiment is included. This paper provides a reference point for researchers to implement different techniques into interdisciplinary iron studies that span cyanobacteria physiology, molecular biology, and biogeochemistry